An in vitro model to test relative antioxidant potential: ultraviolet-induced lipid peroxidation in liposomes.
Since antioxidants have been shown to play a major role in preventing some of the effects of aging and photoaging in skin, it is important to study this phenomenon in a controlled manner. This was accomplished by developing a simple and reliable in vitro technique to assay antioxidant efficacy. Inhibition of peroxidation by antioxidants was used as a measure of relative antioxidant potential. Liposomes, high in polyunsaturated fatty acids (PUFA), were dispersed in buffer and irradiated with ultraviolet (UV) light. Irradiated liposomes exhibited a significantly higher amount of hydroperoxides than liposomes containing antioxidants in a dose- and concentration-dependent manner. Lipid peroxidation was determined spectrophotometrically by an increase in thiobarbituric acid reacting substances. To further substantiate the production of lipid peroxides, gas chromatography was used to measure a decrease in PUFA substrate. In order of decreasing antioxidant effectiveness, the following results were found among lipophilic antioxidants: BHA greater than catechin greater than BHT greater than alpha-tocopherol greater than chlorogenic acid. Among hydrophilic antioxidants, ascorbic acid and dithiothreitol were effective while glutathione was ineffective. In addition, ascorbic acid was observed to act synergistically with alpha-tocopherol, which is in agreement with other published reports on the interaction of these two antioxidants. Although peroxyl radical scavengers seem to be at a selective advantage in this liposomal/UV system, these results demonstrate the validity of this technique as an assay for measuring an antioxidant's potential to inhibit UV-induced peroxidation.
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Estee Lauder Research and Development, Melville, New York 11747.
Maes
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Padulo
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Kim
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Smith
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D000975:Antioxidants / Q000494:pharmacology*; D002849:Chromatography, Gas; D007700:Kinetics; D015227:Lipid Peroxidation / Q000187:drug effects / Q000528:radiation effects*; D008081:Liposomes; D008855:Microscopy, Electron, Scanning; D010713:Phosphatidylcholines; D013053:Spectrophotometry; D014466:Ultraviolet Rays
D000975:Antioxidants; D008081:Liposomes; D010713:Phosphatidylcholines